Shaft kiln



Nov. 28, 1967 w. w. CAMPBELL ET AL 3,355,158

SHAFT KILNv Filed April 2e, v196e Z ONE /A/l/EWT/PS. w/L 14M m @Af/P55,CARL E. R055/ d W WML/4M /e 6000 @SMMM United States Patent O 3,355,158SHAFT KILN William W. Campbell, Carl E. Rossi, and William R. Good,Ludington, Mich., assignors to Harbison-Walker Refractories Company,Pittsburgh, Pa.

Filed Apr. 26, 1966, Ser. No. 545,360 4 Claims. (Cl. 263-29) ABSTRACT OFTHE DISCLOSURE In a shaft kiln hot zone, short and elongate burnerspositioned throughout the zone, the elongate burners being water cooledand having spaced ports over the burners, the ports arranged to open onthe exterior of the burner on substantially the lower 180 degreesthereof.

A shaft kiln is a refractory and metal structure which defines a long,narrow, hollow column or shaft through which raw materials may be passedto be burned. A raw material is charged at the top of the shaft kiln,and it passes progressively downward through preheating, calcining orsintering and cooling zones. Air for combustion and heat transfer isintroduced =at the bottom of the kiln and passes, countercurrent to theraw material, upwardly through the kiln. Therefore, the cooling zone islocated near thetop of the kiln, the burning Zone is located centrally,and the cooling zone is located near the bottom of the shaft. Fuel,generally gas, is introduced through various burners located in thecalcining or sintering zone.

A primary desirable feature of a shaft kiln is its thermal efficiency.This thermal efficiency results because burned materials transfer mostof their heat to incoming air before being discharged, and exhaust gasestransfer most of their heat to incoming raw material before escapingfrom the shaft kiln. If a shaft kiln was long enough, the exhaust gasesand discharge materials could leave -at the same temperature theyentered. Then if there were no heat losses through the side of the shaftkiln, it would operate as a perpetual-motion machine. It is, of course,impossible to prevent heat losses through the sides of the shaft kiln,and it is impractical to make the shaft kiln long enough to completelycool the exhaust gases and discharge material. Nevertheless, it is stilla primary object of shaft kiln operation to effect the most efficientheat transfer.

Channeling of air and gas, especially along the walls of the shaft kiln,results in very poor kiln efficiency. One method of improving the heattransfer in a shaft kiln is to move the combustion air and fueluniformly throughout the charge material within the shaft kiln column sothat heat created by the combustion of the fuel and air is transferredas much as possible t-o the charge and not to the shaft kiln walls. Onetechnique for reducing channeling and promoting uniform treatment of thecharge is to be found disclosed in United States Patent No. 3,165,- 304,assigned to the same assignee as the present case. That patent isconcerned with the introduction of combustion air into the bottom of theshaft kiln.

It is an object of this invention to provide burners placed so that thefuel is more evenly distributed throughout the hot zone, therebyeffecting more uniform heat transfer. It is another object of thisinvention to provide elongate, water-cooled burner construction forplacing fuel uniformly within the sintering zone of a shaft kiln.Another object of the invention is to provide improved shaft kilnconstruction including a novel arrangement of burners.

Briefly, according to one aspect of this invention, a shaft kiln isprovided having elongate, water-cooled burners extending into thesintering zone. These burners have spaced ports over the portion of theburner within the sintering zone arranged to open on the exterior of theburner so that they will not be plugged with falling dust. According toanother aspect of this invention, an elongate burner is provided havinga coupling end which positioned exterior a shaft kiln and a port end forpositioning within the sintering zone of a shaft kiln. The burner iscomprised of three elongate chambers, one being a fuel chamber and beingsubstantially surrounded by two other chambers which are joined at theport end to constitute a water jacket. The fuel chamber has portsextending outward therefrom in communication with the exterior of theburner. The ports are spaced over the port end of the burner andarranged to open on the exterior of the burner so they will not beplugged by falling dust.

Other objects and further features and advantages of this invention willbecome readily apparent to those skilled in the art from a study of thefollowing detailed description with reference to the appended drawings.In these drawings:

FIG. l is a schematic front elevation in section of a shaft kilnembodying the concepts of this invention;

FIG. 2 is a plan 'section taken along line A-A in FIG. 1;

FIG. 3 is a front elevation in section of an elongate burner accordingto the concepts of this invention;

FIG. 4 is -a sectioned end view of the burner taken along the line C C;and

FIG. 5 is a sectioned end view of the burner taken along line D-D.

FIG. 1 shows a front elevation in section of a shaft kiln embodying theconcepts of this invention (the section is along the line B-B shown inFIG. 2). The shaft kiln has an inlet 10 and an outlet 11 which enablethe passage of the charge through the shaft or column 12. The shaft isdefined by a refractory lining or wall 14 held within an outer steelshell 15.

The shaft is preferably ovaloid in section, as shown in FIG. 2, tominimize the distance from the center of the charge and nearest Wall. Tofacilitate this detailed description, approximate dimensions for aparticular shaft kiln are given as follows: The shaft is about 2.0 ft.tall, the short axis of the oval cross-section is about 2 ft., and thelong axis about 8 ft. At the lower end of the shaft kiln is a plenumchamber 16 containing a combustion air inlet 18 and an air-tight valve19 for removing the charge. The plenum chamber enables a positivepressure to be maintained at the discharge end 11 of the shaft kiln. Thepreheating, burning, and cooling zones are labeled on FIG. 1.

The burning zone contains a plurality of spaced rows of burners 20. Therows are spaced about 2 feet apart. Each row contains a plurality ofburners spaced more or less uniformly about the circumference of theshaft kiln. An exemplary arrangement of burners within a row is shown inFIG. 2. According to this invention, -at least one elongate water-cooledburner extends into the hot zone. Preferably, a plurality of elongate,water-cooled burners are spaced substantially alternately with shortburners about a row so that the passage of charge through the shaft kilnis not substantially interrupted. This arrangement is shown in FIG. 2,the elongate burners being labeled 20-L and the normal burners beinglabeled 2li-S. By short burners, we mean burners which do not extendinto the shaft kiln, but deliver fuel to the edge of the charge. It ispreferable if the elongate burners extend about one foot or abouthalfway into the shaft kiln.

An optimal arrangement of burners, which provides maximum fueldistribution with minimum obstruction to descending charge, has beenfound in pairs of elongate and short burners positioned within rowssubstantially opposite each other generally perpendicular to the longaxis of the ovaloid cross-section. The elongate burners extend to aboutthe long axis. The pairs are arranged so that moving around a rowelongate land short burners substantially alternate. lf more than onerow of burners is used, the pairs of burners should be arranged so that,moving vertically, substantially aligned elongate and short burnersalternate.

FIG. 3 is a front section of a water-cooled elongate burner used in thepractice of this invention. The burner has an outer shell or perimeter21 and an inner shell 22 which, along with webs 23, dene three chambers.Two chambers 24 and 25 substantially surround the third chamber 26. Thesurrounding chambers 24 and 2S constitute a water jacket for the innerchamber 26, which is the fuel chamber. The fuel chamber has ports 28which pass through the webs and are in communication With the outside ofthe burner and spaced along the end of the burner to be positionedwithin the hot zone, hereafter referred to as the port end. The portsare arranged to open on the surface of the burner so that they will notbe clogged with falling dust, that is, on substantially the lower 180degrees of the burner. It is also preferable that the ports open to thesides of the burner so that combustion will not take place along theunderside of the burner. The burner is provided with means 29 whichenables it to be fastened to the shell 15 of the shaft kiln. This meansmay comprise a flange 30 welded to the burner containing an opening 31whereby it can be bolted to a similar ange 32 which is threadablyattached to la spacer 34, which spacer is threadably attached to theshell of the shaft kiln 15. The burner also comprises means forintroducing and removing cooling water 35 and 36. This means usuallycomprises threaded nipples for attaching a Water source. The burnerfurther includes means 38 usually threaded for attaching the gas source.

According to this invention, g-as is introduced into the center of theburning zone by the elongate burners through the spaced ports. In thismanner, combustion is substantially moved away from the walls of theshaft kiln. Better heat transfer is promoted and channeling issubstantially prevented. Before the introduction of the elongateburners, we found that about 2 to 21/2 million B.t.u.s per ton ofmagnesite were required for dead burning. Furthermore, the refractorylining 14 had to be replaced on the average of about every three or fourmonths. After the introduction of the elongate burners, it was foundthat only 1 to 11/2 million B.t.u.s per ton of charge was required, andthe lining was in good repair longer than in previous experience. Thefuel and refractory lining saved provides a much more economicoperation.

We have found that the outer shell 21 may be suitably fabricated from a11/2 diameter schedule 40 pipe. The inner shell may be fabricated from a2%1" diameter schedule 40 pipe. One method of fabricating the burner isto divide the pipe used as the outer shell in two parts. The two halvesare milled to accept the webs 23 which are welded to the inner shell 22.The two halves and the webs are then assembled and welded together. Theparts extending outwardly from the inner shell 21 can be M3 holesdrilled through the webs and the inner shell. Burners made accordinglycan be extended at least one foot into the shaft kiln without being bentor distorted appreciably Iby the downward-moving charge.

Having thus described the invention in detail land with sucientparticularity as to enable those skilled in the art to practice it, whatis desired to have protected by Letters Patent is set forth in the.following claims:

We claim:

1. In a vertical shaft kiln including means defining preheating, deadVburning, and' cooling zones in which a raw/ material charge moves fromtop to the bottom, the im provement comprising short and elongateburners posi-- tioned in spaced rows throughout the dead burning zone:and extending into said dead burning'zone, the elongate: burners beingwater cooled and positioned alternately/ with short burners so that thedownward ow of the: charge is not interrupted substantially, saidelongate: burners having ports spaced over the portion of the burnerswithin the dead burning zone, said ports arranged to open on theexterior of the burner on substantially the lower degrees thereof.

2. The vertical shaft kiln according to claim 1 having an ovaloidcross-section and pairs of elongate and short burners positioned withinspaced rows, said pairs beingv substantially opposite each other andgenerally perpendicular to the long axis of the ovaloid cross-section,said elongate burners extending to about the long axis, said pairs beingarranged so that moving horizontally around a row or vertically betweenrows substantially aligned elongate and short burners alternate.

3. An elongate burner for use in a shaft kiln having a coupling end anda port end comprising :means defining three elongate chambers, one beinga fuel chamber substantially surrounded by the other two chambers, saidsurrounding chambers being in communication at the port end andconstituting a water jacket, the means forming the water jacketincluding webs, said Webs extending between the means defining the fuelchamberl and the outer perimeter of the water jacket, and there being aplurality of ports extending from the fuel chamber through the webs andin communication with the exterior of the burner, said ports beingspaced over the port end of the burner and on substantially the lower180 degrees thereof, means on the burner for connecting the coupling endof the fuel chamber to a fuel source, means on the burner for connectingwith water jacket to a water source, and means on the burner forlattaching it to the shaft kiln.

4. The burner according to claim 3 in which the ports open on the sidesof the .burner such thatl combustion does not take place along theunderside of the burner.

References Cited UNITED STATES PATENTS 1,185,205 5/1916 Kemp et al.234-1323 1,660,866 2/1928 Dieu v 234-132 1,950,015 3/1934 Winder et al.234-1323 X 2,108,118 2/ 1938 Greenawalt 263-30 X 2,408,282 9/ 1946 Wolf157-73 X 2,491,705 12/1949 Bloom 158-73 2,933,297 4/ 1960 Erasmus et al.263-30 3,260,514 7/1966 Asano .et a1. 263-30 JAMES W. WESTHAVER, PrimaryExaminer.

JOHN J. CAMBY, Examiner.

1. IN A VERTICAL SHAFT KILN INCLUDING MEANS DEFINING PREHEATING, DEADBURNING, AND COOLING ZONES IN WHICH A RAW MATERIAL CHARGE MOVES FROM THETOP TO THE BOTTOM, THE IMPROVEMENT COMPRISING SHORT AND ELONGATE BURNERSPOSITIONED IN SPACED ROWS THROUGHOUT THE DEAD BURNING ZONE AND EXTENDINGINTO SAID DEAD BURNING ZONE, THE ELONGATE BURNERS BEING WATER COOLED ANDPOSITIONED ALTERNATELY WITH SHORT BURNERS SO THAT THE DOWNWARDLY FLOW OFTHE CHARGE IS NOT INTERRRUPTED SUBSTANTIALLY, SAID ELONGATE BURNERSHAVING PORTS SPACED OVER THE PORTION OF THE BURNERS WITHIN THE DEADBURNING ZONE, SAID PORTS ARRANGED TO OEN ON THE INTERIOR OF THE BURNERON SUBSTANTIALLY THE LOWER 180 DEGREES THEREOF.